Seattle, WA 98117 Frost Dates
Frost dates for Seattle, WA, ZIP 98117
Around 03/08 is the usual last spring frost, about 192 days away. The first fall frost typically arrives around 11/23, about 259 frost-free days later.
Zone 9a (20 to 25°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Seattle, not a forecast for this year.
What to do before the first frost
Zone 9a around Seattle has about 12 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
The actual range around Seattle's last frost
03/08 is the middle of 30 years of NOAA records, not a promise. Plant by 02/13 and you're betting against frost in roughly 9 years out of 10. 03/29 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Seattle compares
At roughly 259 frost-free days, Seattle places 6,510 of 40,283 ZIP codes in this dataset. Within WA, it ranks 26 of 700.
Learn more
zone vs. frost date explains why Zone 9a and Seattle's frost date answer different questions, and the frost range explains how to read the range around Seattle's dates instead of trusting one.